Separation of Binary Mixtures of CO and H₂ by Permeation Through Polymeric Films

Abstract

any modification of the optimal working conditions; then, we have computed the maximal value of the economic criterion that could be reached by modification of the three remaining decision variables: preheater temperature output (t3), bypass Results are presented by means of curves; one can find in Vincent's thesis (1971) numerical values, along with results for other perturbations.Catalyst Activity Decay. The decay of the catalyst activity leads t o a modification of the mathematical expression for the reaction rate R(g,t). TT'hatever this modification, the work of optimization remains the same, our method not being based on the form of R. K e have chosen to simulate this decay by t h e simpler manner which consists of multiplying R by a coefficient a varying from 1 t o 0.5. Figure 3 shows that the economic criterion of the optimally designed sequence is very sensitive to catalyst decay; however, one ran maintain this criterion a t an acceptable level by modifying t3, and AS.Composition at Input. Reaction rate along the reactors depends on the composition of the feed mixture. Figure 4 shows the effect of a variation in the percentage of SOz.One can see that the adjustment of t3, Az, and A 3 is mostappreciable when the percentage of SO2 is decreasing (it has been supposed equal to 7.8 in this project).Total Flow Rate. T h e sequence of reactors has been optimized to produce 50 tons/day of sulfuric acid. Figure 5 shows the results obtained when the production varies from 25 to 75 tons 'day, with and without adjustment of t3, Al, and x3. ConclusionI n a preceding paper we showed that the optimal sequence of reactors was very sensitive to a small variation of preheating temperature (t3). In this paper, we have shown that this sequence is also very sensitive to other perturbations. Severtheless, our method, slightly modified, allows the engineer t o control the reactors to obtain the maximum of the economic criterion, in spite of these perturbations. The method can be implemented on a small process computer.The pure gas permeability coefficients of various polymeric materials to carbon monoxide and hydrogen were determined, and the most promising of these were tested as separation membranes using binary rnixtures of the gases. The effect of temperature, pressure, and feed composition on permeation rate and permeate compositions was determined. Polyimide, Dacron, Parylene C, and caprolactam films proved to be the most effective. Depending on permeator conditions, actual separation factors varying from 14 to about 70 and fluxes varying from 0.03 to 1.3 scfd/ft?were observed. The actual separation and flux were somewhat lower than would b e predicted on the basis of the pure gas studies, assuming Fick's law. All materials tested were selective for hydrogen. Mathematical models of the two limiting cases of ideal permeation stages-i.e., no-mix and perfect-mix stages-were formulated. These models used the experimental flux and permeate compositions which were determined as a function of feed composition for various temp...

Structure/permeability relationships of polyimide membranes. II

“…This monomer was obtained from American Hoechst Corp. of Morristown, NJ. The diamine monomers used were: rnetu-phenylenediamine (rn-PDA) ; 2,4-diaminotoluene ( 2,4-DATr) ; 2,6diaminotoluene ( 2,6-DATr) ; and 3,5-diaminobenzotrifluoride ( 3,. The monomers rn-PDA, 2,4-DATr, and 2,6-DATr were obtained from Aldrich Chemical Co. of Milwaukee, WI, while 3,5-DBTF was obtained from Fluorochem, Ltd. of Old Glossop, Derbyshire, England.…”

Water vapor sorption and transport in dense polyimide membranes

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Gas transport properties of annealed polyimide films

“…After sufficient drying of the films at about mmHg, the apparent amount of gas sorbed in the film at fixed pressure was corrected by subtracting a buoyancy contribution. 1 and decreased by slow cooling as compared with the value for PI-11. This is indicative of a structural change caused by the thermal history.…”